A slot machine having three reels and a mechanism for spinning and stopping them after a starting handle is pulled, in response to control signals from a microprocessor. Each reel has a slotted coding ring forming a single track of digital information which may be read by a single optic sensor as the reel rotates. The track has 32 fields of optical information corresponding to the 32 indicia on its reel. Each field has one slot, the slot width alternating between wide and narrow sides about the track, with one sequence of three narrow slots marking a home position. A position counter counts the number of fields that pass each reel's sensor after the home position. Each time a new field is detected, the reel's direction, speed, acceleration and deceleration are checked, and an error signal is issued if the reel is not spinning properly. When the starting handle is pulled, three random numbers are generated. After a brief delay, the first random number is loaded in a counter and decremented once each time a field on the first reel passes its sensor. When this counter equals zero, a solenoid is fired to stop the first reel's rotation. This procedure is then repeated with the second and third random numbers and reels. After the third reel has stopped, the microprocessor determines whether the numbers stored in the three position counters represents a winning sequence, and notifies the player.